Hernán Cortés, backed by tens of thousands of Tlaxcalan and other Indigenous allies who despised Aztec rule, finally overwhelmed the last defenders of Tenochtitlan on August 13, 1521. Smallpox, famine, and relentless bombardment had already devastated the city. The fall of the Aztec capital opened the way for Spanish colonization of Mexico and reshaped the demographic and political map of the Americas for centuries.
The siege that ended on August 13 had ground on for nearly three months, and by its final days Tenochtitlan was less a city than a charnel house. Smallpox, introduced by the Spanish and their allies, had already killed the emperor Cuitláhuac and tens of thousands of others before the final assault; survivors described corpses piled so thick in the streets that soldiers had to walk across them. Cortés's forces had systematically destroyed the causeways and aqueducts feeding the island city, starving it into submission street by street.
The last emperor, Cuauhtémoc, attempted to escape by canoe across Lake Texcoco but was captured by a Spanish brigantine. Brought before Cortés, he reportedly asked to be killed with the same dagger Cortés wore, saying he had failed to defend his city. Cortés spared him initially, hoping to extract information about hidden Aztec gold—torture and, eventually in 1525, execution followed.
The victory depended overwhelmingly on Indigenous allies: tens of thousands of Tlaxcalans, Texcocans, and other peoples who saw the war as liberation from Aztec tribute and human sacrifice demands, not as conquest by Spain. Their alliance proved decisive and, in the long run, tragic—Spanish colonial rule would prove far harsher than Aztec hegemony had been. Mexico City rose from Tenochtitlan's ruins, built literally atop the old city's stones and canals.